How can I market an idea I feel would be beneficial to parents when shopping with their children?

I have an idea I can picture in my head for a baby/toddler product that parents could use when shopping. I'm unsure where to begin with this idea. I'm also afraid that if I give out the specs, someone else will steal it. Can you help me get started?

Honestly, this isn't what you want to hear, but you can forget that dream of just selling that picture in your head. You don't own it until you have a patent or a business built around it, and even then unless you defend it, ownership is of relatively little value.